(a) Field of the Invention
The present invention relates to a ground fault detecting and controlling method for a parallel-structured high voltage system, and more particularly, such a ground fault detecting and controlling method for a parallel-structured high voltage system, in which it can be more precisely determined whether or not the system operation is emergently stopped based on individual insulation resistance values for respective items of the system, and whether there is the possibility of temporary operation of the system in an emergency stop situation of the system operation.
(b) Background Art
Recently, the spread of electric vehicles (EV), hybrid-electric vehicles (HEV), and other vehicles that rely on electric power has been expanded. Such electrically powered vehicles employ a plurality of items including a battery, which are connected in parallel to one another. In particular, in case of an electric bus high voltage system having a high parallel integration, as shown in FIG. 2, a plurality of items are driven which include 10 batteries, 3 motors and MCUs (Motor Control Units), an accessory inverter, and the like, which are all connected in parallel to one another.
Likewise, in the parallel-structured high voltage system in which the plurality of items are connected in parallel to one another, the measurement of the possibility of a dielectric breakdown of the system is critically important for stability of the system. Conventionally, a main battery management system (BMS) includes a ground fault detecting (GFD) circuit mounted thereon to measure a combined insulation resistance value of the system. Also, although each item of the system includes a separate ground fault detecting circuit, an insulation resistance value of a relevant item is not measured, but the combined insulation resistance value of the system is measured.
Accordingly, such a conventional prior art presents a problem because insulation resistance values of respective items of the parallel-structured system are not measured, but the total combined insulation resistance value of the system is measured. Thus, the possibility of a dielectric breakdown of respective items of the system is not actually measured. Therefore, when the detection of a ground fault is performed through the combined insulation resistance value of the parallel-structured system, even though an insulation resistance value of an individual item drops to less than an individual ground fault reference value (Rρ∈φ), a ground fault situation cannot be accurately determined.
In addition, where an insulation resistance value of an individual item does not drop to less than the individual ground fault reference value (Rref)(i.e., in a situation where a ground fault does not occur), and when the insulation resistance values of all the items are reduced, the combined insulation resistance value of the system may drop to less than a reference value. Accordingly, a ground fault situation of the system is erroneously recognized.
In other words, in a system in which a plurality of items are connected in parallel to one another, a definite criterion for judging the ground fault situation cannot be suggested by only the reference value for the entire system. Thus, the precise control of the system is impossible utilizing the conventional technique.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgment or any form of suggestion that this information forms the prior art that is already known to a person skilled in that art.